Until the formulae of Lindstrom et al. the automatic analysis of electromyograms had no empirical basis in the differentiation of neurapraxia and degenerative paralysis. The EMG-analysis computer program modified by Berg et al. was used for the evaluation of average power spectra derived with a Fast Fourier transformation on 37 patients with known neurapraxia and 54 with proven degeneration. In order to work out a characteristic function we calculated average power spectra separately for each type of paralysis (facial or laryngeal muscles). The resulting spectrum configurations and their absolute values (root-mean-square and central frequency) were compared, and their value in automated EMG analysis was analysed. The results provide a basis for the routine use of the computer program in routine clinical diagnosis.